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Home Garden Lot: Garden & Home Improvement

What Hardiness Zone Is Iowa?

USDA 2023 Plant Hardiness Zone Map · 1,042 ZIP codes · Data updated 2026-10-28

Quick answer

Iowa spans USDA hardiness zones 4b–6a on the 2023 Plant Hardiness Zone Map. The most common zone is 5a, covering 54% of Iowa's ZIP codes, followed by zone 5b (42%). Zone 5a means the coldest night of an average winter reaches −20°F to −15°F (−29°C to −26°C). Enter your ZIP code for your exact zone.

Iowa hardiness zones by share of ZIP codes

Zone 4b2% · 17 ZIPs
Zone 5a54% · 563 ZIPs
Zone 5b42% · 433 ZIPs
Zone 6a3% · 29 ZIPs

What the zones mean for Iowa gardeners

  • Coldest and warmest towns: among towns with NOAA weather stations, Sibley (1,529 ft) is in zone 4b, while Keokuk Lock Dam 19 (527 ft) is in zone 6a. That is a difference of about 15°F in the coldest night of a typical winter.
  • Same zone, different frost dates: within zone 5a, the median last spring frost ranges from April 19 at Dubuque L&d 11 to May 5 at Sheldon, 16 days apart. Your zone tells you which perennials survive winter; your frost dates tell you when to plant.

Typical frost dates in each Iowa zone

Medians across NOAA weather stations in each zone. Colder zones usually have later spring frosts, but local terrain can shift the dates by weeks.

ZoneLast spring frostFirst fall frostStations
4bMay 8October 13
5aApril 30October 787
5bApril 24October 1454
6aApril 15October 225

Hardiness zones for Iowa cities

Zones at the National Weather Service stations, mostly city airports, with their median frost dates.
Ames Municipal Airport5b−15°F to −10°F930Apr 26Oct 8
Burlington Municipal Airport6a−10°F to −5°F692Apr 15Oct 20
Cedar Rapids Municipal Airport5a−20°F to −15°F868Apr 27Oct 11
Davenport5b−15°F to −10°F754Apr 23Oct 15
Des Moines 17 E5b−15°F to −10°F921Apr 21Oct 15
Des Moines Intl Airport5b−15°F to −10°F957Apr 18Oct 20
Dubuque Regional Airport5a−20°F to −15°F1,056Apr 28Oct 11
Estherville Municipal Airport5a−20°F to −15°F1,317May 2Sep 30
Iowa City Municipal Airport5b−15°F to −10°F650Apr 21Oct 18
Lamoni5b−15°F to −10°F1,168Apr 16Oct 20
Lamoni Municipal Airport5b−15°F to −10°F1,131Apr 16Oct 21
Marshalltown Municipal Airport5a−20°F to −15°F974Apr 30Oct 6
Mason City Municipal Airport5a−20°F to −15°F1,225May 3Oct 1
Ottumwa Industrial Airport5b−15°F to −10°F842Apr 23Oct 14
Sioux City Gateway Airport5a−20°F to −15°F1,095Apr 29Oct 5
Spencer Municipal Airport5a−20°F to −15°F1,338May 2Oct 2
Waterloo Municipal Airport5a−20°F to −15°F868Apr 27Oct 10

Hardiness zones for 149 towns in Iowa

Each NOAA weather station is shown with the USDA zone of the nearest ZIP code (within 8 miles). Coldest night is the zone's range for the average annual extreme minimum temperature. Click a column to sort.
Albia 3 NNE5b−15°F to −10°F880Apr 24Oct 16
Algona5a−20°F to −15°F1,214Apr 30Oct 6
Allerton5b−15°F to −10°F1,090Apr 21Oct 19
Allison5a−20°F to −15°F1,038Apr 27Oct 8
Ames 5 SE5b−15°F to −10°F870Apr 26Oct 12
Ames 8 WSW5a−20°F to −15°F1,099Apr 23Oct 14
Ames Municipal Airport5b−15°F to −10°F930Apr 26Oct 8
Anamosa 1 WNW5a−20°F to −15°F805May 1Oct 4
Anamosa 3 SSW5a−20°F to −15°F906Apr 27Oct 13
Ankeny5b−15°F to −10°F975Apr 23Oct 15
Atlantic 1 NE5a−20°F to −15°F1,152Apr 30Oct 2
Audubon5a−20°F to −15°F1,280May 2Oct 3
Battle Creek 3NE5a−20°F to −15°F1,380May 1Oct 1
Beaconsfield5b−15°F to −10°F1,215Apr 23Oct 17
Bedford5b−15°F to −10°F1,190Apr 24Oct 15
Belle Plaine5a−20°F to −15°F810Apr 28Oct 10
Bellevue L&d 125a−20°F to −15°F603Apr 25Oct 16
Bloomfield5b−15°F to −10°F858Apr 16Oct 22
Boone5a−20°F to −15°F1,035Apr 28Oct 12
Britt 3E5a−20°F to −15°F1,220Apr 29Oct 7
Burlington 2S6a−10°F to −5°F690Apr 18Oct 20
Burlington Municipal Airport6a−10°F to −5°F692Apr 15Oct 20
Carroll5a−20°F to −15°F1,240Apr 27Oct 10
Cascade5a−20°F to −15°F814Apr 28Oct 10
Castana Experiment Farm5b−15°F to −10°F1,400Apr 25Oct 12
Cedar Rapids #15a−20°F to −15°F813Apr 28Oct 12
Cedar Rapids Municipal Airport5a−20°F to −15°F868Apr 27Oct 11
Centerville5b−15°F to −10°F905Apr 28Oct 14
Chariton 1 E5b−15°F to −10°F965May 5Oct 5
Charles City5a−20°F to −15°F993Apr 30Oct 6
Cherokee5a−20°F to −15°F1,210May 4Oct 4
Clarinda5b−15°F to −10°F980Apr 25Oct 11
Clarion5a−20°F to −15°F1,156Apr 30Oct 10
Clinton #15b−15°F to −10°F585Apr 22Oct 16
Coggon5a−20°F to −15°F903May 3Oct 7
Colo5a−20°F to −15°F1,000Apr 24Oct 12
Columbus Junction5b−15°F to −10°F590Apr 26Oct 10
Corning5b−15°F to −10°F1,190Apr 27Oct 12
Cresco 1 NE4b−25°F to −20°F1,255May 8Oct 1
Creston 2 SW5b−15°F to −10°F1,296Apr 28Oct 11
Dakota City5a−20°F to −15°F1,110Apr 26Oct 12
Davenport5b−15°F to −10°F754Apr 23Oct 15
Davenport WFO5b−15°F to −10°F750Apr 21Oct 17
Decorah5a−20°F to −15°F860May 3Oct 7
Denison5a−20°F to −15°F1,401Apr 27Oct 11
Des Moines 17 E5b−15°F to −10°F921Apr 21Oct 15
Des Moines Intl Airport5b−15°F to −10°F957Apr 18Oct 20
Des Moines Wsfo-johnston5b−15°F to −10°F959Apr 19Oct 18
Donnellson6a−10°F to −5°F705Apr 17Oct 22
Dubuque L&d 115a−20°F to −15°F620Apr 19Oct 21
Dubuque Regional Airport5a−20°F to −15°F1,056Apr 28Oct 11
Eldora5a−20°F to −15°F1,073Apr 27Oct 10
Elkader 6 SSW4b−25°F to −20°F788May 8Oct 1
Emmetsburg5a−20°F to −15°F1,225Apr 27Oct 7
Estherville 4E5a−20°F to −15°F1,320May 2Oct 3
Estherville Municipal Airport5a−20°F to −15°F1,317May 2Sep 30
Fairfield5b−15°F to −10°F740Apr 27Oct 12
Fayette5a−20°F to −15°F1,145May 4Oct 4
Forest City 2 NNE5a−20°F to −15°F1,280Apr 30Oct 7
Fort Dodge 5NNW5a−20°F to −15°F1,115Apr 28Oct 8
Fort Madison6a−10°F to −5°F530Apr 12Oct 25
Glenwood 3SW5b−15°F to −10°F980Apr 23Oct 11
Greenfield5b−15°F to −10°F1,316Apr 25Oct 12
Grinnell 3 SW5b−15°F to −10°F905May 3Oct 6
Grundy Center5a−20°F to −15°F985Apr 29Oct 9
Guthrie Center5a−20°F to −15°F1,065May 2Oct 3
Guttenberg L&d 105a−20°F to −15°F618Apr 21Oct 18
Hampton5a−20°F to −15°F1,105Apr 29Oct 9
Harlan5b−15°F to −10°F1,270Apr 27Oct 9
Hawarden5a−20°F to −15°F1,190May 1Oct 4
Holstein5a−20°F to −15°F1,370Apr 30Oct 9
Humboldt Wtp5a−20°F to −15°F1,100Apr 27Oct 9
Ida Grove 5NW5a−20°F to −15°F1,320Apr 27Oct 12
Independence #15a−20°F to −15°F1,010Apr 30Oct 7
Indianola 2W5b−15°F to −10°F924Apr 24Oct 12
Iowa City5b−15°F to −10°F640Apr 29Oct 9
Iowa City Municipal Airport5b−15°F to −10°F650Apr 21Oct 18
Iowa Falls5a−20°F to −15°F1,055Apr 28Oct 10
Jefferson5b−15°F to −10°F1,055Apr 26Oct 9
Keokuk Lock Dam 196a−10°F to −5°F527Apr 10Oct 27
Keosauqua5b−15°F to −10°F629Apr 26Oct 13
Knoxville5b−15°F to −10°F895Apr 20Oct 19
Lake Park5a−20°F to −15°F1,465Apr 30Oct 10
Lamoni5b−15°F to −10°F1,168Apr 16Oct 20
Lamoni Municipal Airport5b−15°F to −10°F1,131Apr 16Oct 21
Le Claire L&d 145b−15°F to −10°F577Apr 16Oct 25
Le Mars5a−20°F to −15°F1,195Apr 30Oct 4
Leon 6 ESE5b−15°F to −10°F1,000Apr 30Oct 8
Little Sioux 2 NW5a−20°F to −15°F1,025May 1Oct 3
Logan5b−15°F to −10°F990Apr 29Oct 8
Lowden5a−20°F to −15°F738Apr 27Oct 10
Manchester #25a−20°F to −15°F990May 3Oct 4
Mapleton No.25a−20°F to −15°F1,200May 3Oct 1
Maquoketa5a−20°F to −15°F668Apr 25Oct 14
Marshalltown5a−20°F to −15°F870Apr 28Oct 7
Marshalltown Municipal Airport5a−20°F to −15°F974Apr 30Oct 6
Mason City5a−20°F to −15°F1,105Apr 29Oct 7
Mason City Municipal Airport5a−20°F to −15°F1,225May 3Oct 1
Milford 4 NW5a−20°F to −15°F1,402May 1Oct 6
Mount Ayr5b−15°F to −10°F1,140Apr 25Oct 12
Mount Pleasant 1 SSW5b−15°F to −10°F730Apr 30Oct 10
Muscatine5b−15°F to −10°F549Apr 24Oct 14
Muscatine 2N5b−15°F to −10°F680Apr 18Oct 22
New Hampton5a−20°F to −15°F1,148May 2Oct 5
Newton5b−15°F to −10°F960Apr 22Oct 17
Northwood5a−20°F to −15°F1,190May 4Oct 4
Oakland5b−15°F to −10°F1,260Apr 23Oct 14
Oelwein 1E5a−20°F to −15°F1,165Apr 27Oct 13
Oelwein 2 S5a−20°F to −15°F1,010Apr 30Oct 9
Onawa 3NW5a−20°F to −15°F1,060May 1Oct 3
Osage5a−20°F to −15°F1,170Apr 30Oct 9
Osceola5b−15°F to −10°F1,028Apr 29Oct 9
Oskaloosa5b−15°F to −10°F830Apr 21Oct 16
Ottumwa Industrial Airport5b−15°F to −10°F842Apr 23Oct 14
Perry5a−20°F to −15°F950Apr 25Oct 10
Pocahontas5a−20°F to −15°F1,212Apr 26Oct 7
Postville5a−20°F to −15°F1,165May 1Oct 3
Primghar5a−20°F to −15°F1,520Apr 29Oct 10
Rathbun Dam5b−15°F to −10°F965Apr 18Oct 23
Red Oak5b−15°F to −10°F1,040Apr 24Oct 13
Rock Rapids5a−20°F to −15°F1,350May 1Oct 4
Rockwell City5a−20°F to −15°F1,214Apr 26Oct 10
Sac City5a−20°F to −15°F1,210Apr 30Oct 6
Sanborn5a−20°F to −15°F1,551May 1Oct 7
Sheldon5a−20°F to −15°F1,420May 5Sep 28
Shenandoah5b−15°F to −10°F999Apr 20Oct 17
Sibley4b−25°F to −20°F1,529May 5Oct 3
Sidney 1SSE5b−15°F to −10°F1,140Apr 19Oct 19
Sigourney5b−15°F to −10°F732Apr 24Oct 15
Sioux Center 2 SE5a−20°F to −15°F1,360Apr 30Oct 3
Sioux City Ang5a−20°F to −15°F1,100Apr 29Oct 7
Sioux City Gateway Airport5a−20°F to −15°F1,095Apr 29Oct 5
Sioux Rapids 4 E5a−20°F to −15°F1,420Apr 30Oct 5
Spencer 1 N5a−20°F to −15°F1,326May 1Oct 3
Spencer Municipal Airport5a−20°F to −15°F1,338May 2Oct 2
Spirit Lake5a−20°F to −15°F1,420Apr 28Oct 11
Stanley5a−20°F to −15°F1,114May 4Oct 1
Storm Lake5a−20°F to −15°F1,442Apr 25Oct 13
Swea City 5N5a−20°F to −15°F1,180May 4Oct 1
Tipton5a−20°F to −15°F820Apr 21Oct 15
Toledo 3N5a−20°F to −15°F935Apr 30Oct 9
Tripoli5a−20°F to −15°F1,055Apr 29Oct 9
Vinton5a−20°F to −15°F850May 3Oct 3
Washington5b−15°F to −10°F687Apr 28Oct 11
Waterloo Municipal Airport5a−20°F to −15°F868Apr 27Oct 10
Waukon5a−20°F to −15°F1,275May 2Oct 11
Webster City5a−20°F to −15°F1,072May 3Oct 2
Williamsburg 1E5b−15°F to −10°F780Apr 28Oct 9
Winterset 1S5b−15°F to −10°F1,100Apr 30Oct 3

Frequently asked questions

What hardiness zone is Iowa?

Iowa is in USDA hardiness zones 4b–6a on the 2023 USDA Plant Hardiness Zone Map. Zone 5a is the most common, covering 54% of Iowa's ZIP codes, and zone 5b covers 42%. Enter your ZIP code for your exact zone.

What does zone 5a mean?

Zone 5a means the average annual extreme minimum temperature, the coldest night of a typical winter, is −20°F to −15°F (−29°C to −26°C). Perennials, shrubs and trees rated for zone 5a or colder should survive winter there.

What is the coldest hardiness zone in Iowa?

Zone 4b is the coldest zone mapped in Iowa, found around Sibley, and zone 6a is the warmest, found around Keokuk Lock Dam 19.

Did Iowa's hardiness zones change in 2023?

The USDA released a new Plant Hardiness Zone Map in November 2023, based on 1991–2020 temperatures instead of 1976–2005. About half of the United States shifted half a zone warmer. Check your ZIP code here, because plant tags and older books may still list your 2012 zone.

When should I plant in zone 5a?

Hardiness zones don't set planting dates; frost dates do. Inside zone 5a in Iowa, the median last spring frost varies from April 19 to May 5. Look up your local frost dates and plant tender crops such as tomatoes after the 10%-risk last-frost date.

Zone and frost dates: use both

Your hardiness zone answers one question: will this plant survive the winter here? Choose perennials, shrubs, trees and bulbs rated for your zone or a colder one. For vegetables and annuals, what matters is the length of the frost-free season. See Iowa frost dates by town, or get a planting calendar for your ZIP code with start-indoors, transplant and sowing dates for 30 crops.

Sources and method

Zones are from the USDA 2023 Plant Hardiness Zone Map ZIP-code files published by the PRISM Climate Group, Oregon State University, based on 1991–2020 minimum temperatures. ZIP codes are assigned to states by USPS prefix. Town zones use the ZIP code nearest each NOAA 1991–2020 Climate Normals station. This is an independent tool, not an official USDA site. Full methodology.

Hardiness zones in other states